1. Field of the invention
The present invention relates to a bearing device which is press-fitted between the inside surface of the axis insertion hole of a housing like a steering column and the outside surface of a steering axis or the like inserted into the axis insertion hole, so as to support the axis.
2. Description of the Related Art
The steering axis in an automobile steering mechanism is linked between a steering wheel and a universal joint, and supported by a roller bearing inside the axis insertion hole of the steering column.
While roller bearings are manufactured by bearing manufacturer""s, steering axes and steering columns are manufactured by automobile makers.
The bearing manufacturers have a desire to use a roller bearing having the same specification as a steering axis which is supported by the roller bearing.
The steering axes have an approximately united outer diameter in each automobile maker; however, the steering columns have different inner diameters in each maker.
For this reason, the clearance in the radius direction between the outside surface of the steering axis and the inside surface of the axis insertion hole of the steering column is not fixed.
Therefore, in order to support the steering axis inside the axis insertion hole of the steering column by a roller bearing, a spacer ring is needed to adjust the clearance formed in the radial direction.
FIG. 13 shows the structure of the main part of the automobile steering mechanism where a steering axis is linked between a steering wheel and the universal joint.
The steering axis 50 is inserted into the axis insertion hole of a steering column 51. The steering axis 50 is supported in a rotatable manner by a bearing device 52 inside the axis insertion hole of the steering column 51.
The bearing device 52 is composed of a roller bearing 53 and a spacer ring 54 for adjusting the clearance in the radius direction. The spacer ring 54 is made from an elastic material like rubber in order to enhance the steering sense.
The spacer ring 54 is press-fitted into the clearance in the radius direction between the steering axis 50 and the steering column 51 by taking advantage of its elasticity. In this case, the larger the inner diameter of the axis insertion hole of the steering column 51 to increase the clearance in the radius direction, the thicker the wall of the spacer ring 54 becomes. The spacer ring 54 having a thick wall is a kind of stiffened member even if it is made from an elastic material like rubber.
Therefore, when the axis insertion hole of the steering column 51 has, for example, too small an inner diameter due to the variations during manufacturing, the spacer ring 54 stiffened with the thick wall makes it hard for the roller bearing 53 to be well incorporated into the spacer ring 54 by taking advantage of its elastic deformation. As a result, the efficiency of the assembly operation is badly affected, resulting in a rise in production cost.
Such a problem is not limited to automobiles having a steering column, but holds true in a bearing device which is press-fitted between the inside surface of the axis insertion hole of a housing or the like and the outside surface of an axis inserted into the axis insertion hole so as to support the axis, when there are variations in the inner diameter of the axis insertion hole during manufacturing, and a spacer ring made from an elastic material is used to support the axis.
Therefore, a main object of the present invention is to provide a bearing device which can be easily applied into the clearance formed in the radius direction between a housing and an axis even if there are variations in the inner diameter of the axis insertion hole of the housing.
Other objects, features and advantages of the present invention will be clarified in the following description.
In the present invention, a bearing device is incorporated into a mechanism comprising a housing having an axis insertion hole and an axis to be inserted into said axis insertion hole, and which supports said axis inside said housing, and the bearing device comprises a roller bearing arranged on an external circumference of said axis; and a spacer ringmade from an elastic material and arranged between an outside surface of said roller bearing and an inside surface of said axis insertion hole of said housing. The spacer ring comprises a wall thickness holding unit for holding thickness of a wall thereof in a radius direction; and a thickness reduction unit which is provided in a vicinity of said wall thickness holding unit and which reduces the thickness of the wall in the radius direction to facilitate deformation of said spacer ring.
Preferably, said spacer ring has a concavo-convex portion on an outside surface thereof in an axial direction, and said thickness reduction unit composed of said concavo-convex portion comprises an elastic deformation unit which deforms in accordance with an acting force applied in the radius direction from the inside surface of said axis insertion hole, depending on an inner diameter of said axis insertion hole.
Preferably, said housing has a holding hook which protrudes inwardly in the radius direction, and said thickness reduction unit is capable of being held by said holding hook.
Preferably, said spacer ring comprises a through hole formed in the axial direction and circular seals arranged on both ends of an internal wall thereof, and further comprises a roller bearing storage unit at a center in the axial direction, and said roller bearing is stored in said roller storage unit of said spacer ring.